Solid-state imaging device with phase difference detection pixel and manufacturing method of the same, and electronic apparatus

ABSTRACT

There is provided a solid-state imaging device including: an imaging pixel including a photoelectric conversion unit which receives incident light; and a phase difference detection pixel including the photoelectric conversion unit and a light shielding unit which shields some of the light incident to the photoelectric conversion unit, in which the imaging pixel further includes a high refractive index film which is formed on the upper side of the photoelectric conversion unit, and the phase difference detection pixel further includes a low refractive index film which is formed on the upper side of the photoelectric conversion unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/567,080, filed Dec. 11, 2014, which claims the benefit of JapanesePatent Application No. JP 2013-260785, filed Dec. 18, 2013, and JapanesePatent Application No. JP 2014-067809, filed Mar. 28, 2014, the entiredisclosures of which are hereby incorporated herein by reference.

BACKGROUND

The present technology relates to a solid-state imaging device and amanufacturing method of the same, and an electronic apparatus, andparticularly relates to a solid-state imaging device and a manufacturingmethod of the same, and an electronic apparatus which can optimizesensitivity of an imaging pixel and AF performance of a phase differencedetection pixel.

In the related art, regarding the solid-state imaging device, varioustechnologies have been proposed, in order to realize improvement ofsensitivity or prevention of color mixture.

For example, a solid-state imaging device in which a lens layer of whicha portion corresponding to the center of a light receiving surface isformed with a refractive index distribution lower than that of a portioncorresponding to a periphery of the light receiving surface, is formedas a diverging lens which allows a light condensing point of an incidentlight from an on-chip lens to approach the light receiving surface, ineach pixel, has been proposed (for example, see Japanese UnexaminedPatent Application Publication No. 2011-210981). Therefore, it ispossible to shorten a distance between the on-chip lens and the lightreceiving surface, and to realize improvement of sensitivity orprevention of color mixture.

However, in the related art, in a digital single lens reflex camera(DSLR), since focusing is performed by a sensor which is providedseparately from a solid-state imaging device which captures an image,the number of components increases or focusing is performed in aposition different from a position where focusing is actually desired,and thus an error may occur regarding the focusing position.

Meanwhile, in recent years, there has been known a solid-state imagingdevice which provides phase difference detection pixels with imagingpixels in a pixel array unit, and detects focusing based on a shiftamount of signals output by the pair of phase difference detectionpixels, that is, performs focus detection by an image plane phasedifference auto focus (AF) system. In the pair of phase differencedetection pixels, a half of each light receiving surface different fromone another is shielded by a light shielding film.

SUMMARY

In the solid-state imaging device described above, when a condensingpoint of a microlens is on a light receiving surface of a photoelectricconversion unit which is a lower layer than a light shielding film,sensitivity of an imaging pixel becomes maximum, whereas, when acondensing point of a microlens is on a light shielding film, AFperformance of a phase difference detection pixel becomes maximum.

However, when optimizing the sensitivity of the imaging pixel, thesensitivity of the phase difference detection pixel may decrease, andparticularly when a subject is dark, it is difficult to accuratelyperform focusing.

It is desirable to optimize sensitivity of an imaging pixel and AFperformance of a phase difference detection pixel.

According to an embodiment of the present technology, there is provideda solid-state imaging device including: an imaging pixel including aphotoelectric conversion unit which receives incident light; and a phasedifference detection pixel including the photoelectric conversion unitand a light shielding unit which shields some of the light incident tothe photoelectric conversion unit, in which the imaging pixel furtherincludes a high refractive index film which is formed on the upper sideof the photoelectric conversion unit, and the phase difference detectionpixel further includes a low refractive index film which is formed onthe upper side of the photoelectric conversion unit.

In the embodiment, the imaging pixel and the phase difference detectionpixel may include color filter layers which are respectively formed onupper layers of the high refractive index film and the low refractiveindex film, and the high refractive index film and the low refractiveindex film may function as a flattening film.

In the embodiment, the low refractive index film may be formed to coverthe high refractive index film and function as the flattening film.

In the embodiment, the high refractive index film may be formed to coverthe low refractive index film and function as the flattening film.

In the embodiment, a refractive index of the high refractive index filmmay be higher than a refractive index of the low refractive index film,by a value equal to or greater than 0.1.

In the embodiment, the refractive index of the high refractive indexfilm may be set as a value from 1.5 to 2.0.

In the embodiment, the refractive index of the low refractive index filmmay be set as a value from 1.1 to 1.5.

In the embodiment, any one or both of the high refractive index film andthe low refractive index film may be formed of a material having aphotosensitive property.

In the embodiment, the high refractive index film or the low refractiveindex film may be formed to have a cross-sectional shape as a shape of aconvex lens.

In the embodiment, the imaging pixel and the phase difference detectionpixel may include microlenses on the upper side of the color filterlayers, and the microlenses may be formed in the same manner, in theimaging pixel and the phase difference detection pixel.

According to another embodiment of the present technology, there isprovided a manufacturing method of a solid-state imaging device whichincludes an imaging pixel including a photoelectric conversion unitwhich receives incident light, and a phase difference detection pixelincluding the photoelectric conversion unit and a light shielding unitwhich shields some of the light incident to the photoelectric conversionunit, the method including: forming a high refractive index film on theupper side of the photoelectric conversion unit in the imaging pixel;and forming a low refractive index film on the upper side of thephotoelectric conversion unit in the phase difference detection pixel.

According to still another embodiment of the present technology, thereis provided an electronic apparatus including: a solid-state imagingdevice including an imaging pixel including a photoelectric conversionunit which receives incident light; and a phase difference detectionpixel including the photoelectric conversion unit and a light shieldingunit which shields some of the light incident to the photoelectricconversion unit, wherein the imaging pixel further includes a highrefractive index film which is formed on the upper side of thephotoelectric conversion unit, and the phase difference detection pixelfurther includes a low refractive index film which is formed on theupper side of the photoelectric conversion unit.

In the embodiment, the high refractive index film is formed on the upperside of the photoelectric conversion unit in the imaging pixel, and thelow refractive index film is formed on the upper side of thephotoelectric conversion unit in the phase difference detection pixel.

In the embodiment, it is possible to optimize sensitivity of the imagingpixel and AF performance of the phase difference detection pixel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration example of asolid-state imaging device to which the present technology is applied;

FIG. 2 is a diagram illustrating a pixel arrangement of a pixel arrayunit;

FIG. 3 is a cross-sectional view showing a configuration example of apixel of a first embodiment of the present technology;

FIG. 4 is a flowchart illustrating a pixel formation process;

FIGS. 5A to 5C are diagrams illustrating a pixel formation step;

FIGS. 6A to 6C are diagrams illustrating a pixel formation step;

FIG. 7 is a cross-sectional view showing another configuration exampleof a pixel;

FIG. 8 is a cross-sectional view showing a configuration example of apixel of a second embodiment of the present technology;

FIG. 9 is a flowchart illustrating a pixel formation process;

FIGS. 10A to 10D are diagrams illustrating a pixel formation step;

FIGS. 11A to 11C are diagrams illustrating a pixel formation step;

FIG. 12 is a cross-sectional view showing a configuration example of apixel of a third embodiment of the present technology;

FIG. 13 is a flowchart illustrating a pixel formation process;

FIGS. 14A to 14D are diagrams illustrating a pixel formation step;

FIGS. 15A to 15C are diagrams illustrating a pixel formation step;

FIG. 16 is a flowchart illustrating a pixel formation process;

FIGS. 17A to 17D are diagrams illustrating a pixel formation step;

FIGS. 18A to 18C are diagrams illustrating a pixel formation step;

FIG. 19 is a cross-sectional view showing a configuration example of apixel of a fourth embodiment of the present technology;

FIG. 20 is a flowchart illustrating a pixel formation process;

FIGS. 21A to 21D are diagrams illustrating a pixel formation step;

FIGS. 22A to 22D are diagrams illustrating a pixel formation step;

FIG. 23 is a cross-sectional view showing a configuration example of apixel of a fifth embodiment of the present technology;

FIG. 24 is a diagram showing an example of a color filter;

FIG. 25 is a cross-sectional view showing a configuration example of apixel of a sixth embodiment of the present technology;

FIG. 26 is a flowchart illustrating a pixel formation process;

FIGS. 27A to 27D are diagrams illustrating a pixel formation step;

FIGS. 28A to 28C are diagrams illustrating a pixel formation step;

FIG. 29 is a diagram illustrating an exposure pattern of a reticle;

FIG. 30 is a diagram illustrating an exposure pattern of a reticle;

FIG. 31 is a flowchart illustrating a pixel formation process;

FIGS. 32A to 32D are diagrams illustrating a pixel formation step;

FIG. 33 is a diagram illustrating an exposure pattern of a gray scalemask;

FIG. 34 is a cross-sectional view showing a configuration example of apixel of a seventh embodiment of the present technology;

FIG. 35 is a diagram showing another example of a color filter; and

FIG. 36 is a block diagram showing a configuration example of anelectronic apparatus to which the present technology is applied.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present technology will be describedwith the drawings.

Configuration Example of Solid-State Imaging Device

FIG. 1 is a block diagram showing one embodiment of a solid-stateimaging device to which the present technology is applied. Hereinafter,a configuration of a surface irradiation type complementary metal oxidesemiconductor (CMOS) image sensor which is an amplification typesolid-state imaging device will be described. The present technology isnot limited to be applied to the surface irradiation type CMOS imagesensor, but can also be applied to the rear surface irradiation typeCMOS image sensor, another amplification type solid-state imagingdevice, or a charge transfer type solid-state imaging device such as acharge coupled device (CCD) image sensor.

A CMOS image sensor 10 shown in FIG. 1 includes a pixel array unit 11which is formed on a semiconductor substrate (not shown), and aperipheral circuit unit which is integrated on the semiconductorsubstrate in the same manner as the pixel array unit 11. The peripheralcircuit unit is, for example, configured with a vertical driving unit12, a column processing unit 13, a horizontal driving unit 14, and asystem control unit 15.

The CMOS image sensor 10 further includes a signal processing unit 18and a data storage unit 19.

The pixel array unit 11 has a configuration in that unit pixels(hereinafter, also simply referred to as pixels) including aphotoelectric conversion unit which generates and stores photoelectriccharges according to received light intensity, are arranged in a rowdirection and a column direction, that is, two-dimensionally in amatrix. Herein, the row direction indicates an arrangement direction ofpixels in a pixel row (horizontal direction), and the column directionindicates an arrangement direction of pixels in a pixel column (verticaldirection). In the pixel array unit 11, pixels (imaging pixels) forgenerating a signal for generating a captured image based on receivedsubject light, and pixels (phase difference detection pixels) forgenerating a signal for performing focus detection are arranged as aplurality of pixels.

In the pixel array unit 11, a pixel driving line 16 is wired along therow direction for each pixel row, and a vertical signal line 17 isarranged along the column direction for each pixel column, with respectto a pixel arrangement in a matrix. The pixel driving line 16 transmitsa driving signal for performing driving when reading out a signal from apixel. In FIG. 1, the pixel driving line 16 is shown as one wire, but isnot limited to one wire. One end of the pixel driving line 16 isconnected to an output end corresponding to each row of the verticaldriving unit 12.

The vertical driving unit 12 is configured with a shift register or anaddress decoder, and drives the entirety of pixels of the pixel arrayunit 11 at the same time, or each pixel thereof in a line unit. That is,the vertical driving unit 12 configures a driving unit which drives eachpixel of the pixel array unit 11, with a system control unit 15 whichcontrols the vertical driving unit 12. The specific configuration of thevertical driving unit 12 is omitted in the drawing, but the verticaldriving unit is generally configured to have two scanning systems of aread-out scanning system and a sweep-out scanning system.

The read-out scanning system sequentially selects and scans the unitpixel of the pixel array unit 11 in the row unit, in order to read out asignal from the unit pixel. The signal read out from the unit pixel isan analog signal. The sweep-out scanning system performs sweep-outscanning prior to read-out scanning by the time of a shutter speed, withrespect to a read-out row where the read-out scanning is performed bythe read-out scanning system.

The unnecessary charges are swept out from the photoelectric conversionunit of the unit pixel in the read-out row by performing the sweep-outscanning by the sweep-out scanning system, and accordingly thephotoelectric conversion unit is reset. Since the unnecessary chargesare swept out (reset) by this sweep-out scanning system, an electronicshutter operation is performed. Herein, the electronic shutter operationis an operation of deleting photoelectric charges of the photoelectricconversion unit and newly starting exposure (starting storage ofphotoelectric charges).

The signal read out by the read-out operation by the read-out scanningsystem corresponds to light intensity received after the previousread-out operation or the electronic shutter operation. A time periodfrom a read-out timing by the previous read-out operation or from asweep-out timing by the electronic shutter operation to a read-outtiming of current read-out operation, is an exposure time period of thephotoelectric charges of the unit pixel.

The signal output from each unit pixel of the pixel row which isselected and scanned by the vertical driving unit 12, is input to thecolumn processing unit 13 through each of the vertical signal line 17for each pixel column. The column processing unit 13 performs apredetermined signal process with respect to the signal output throughthe vertical signal line 17 from each pixel in the selected row, foreach pixel column of the pixel array unit 11, and temporarily holds thepixel signal after the signal process.

Specifically, the column processing unit 13 at least performs a noiseremoving process, for example, correlated couple sampling (CDS) process,as a signal process. The fixed pattern noise unique to a pixel, such asreset noise or variation of a threshold value of an amplificationtransistor in the pixel, is removed by the CDS process by the columnprocessing unit 13. In addition to the noise removing process, thecolumn processing unit 13 has an analog-digital (AD) conversionfunction, for example, and can also convert an analog pixel signal intoa digital signal and output the digital signal.

The horizontal driving unit 14 is configured with a shift register or anaddress decoder, and sequentially selects the unit circuit correspondingto the pixel column of the column processing unit 13. The pixel signalsubjected to the signal processing for each unit circuit by the columnprocessing unit 13 is sequentially output by the selection scanning bythe horizontal driving unit 14.

The system control unit 15 is configured with a timing generator whichgenerates various timing signals, and performs driving control of thevertical driving unit 12, the column processing unit 13, and thehorizontal driving unit 14, based on the various timing signalsgenerated by the timing generator.

The signal processing unit 18 has at least an arithmetic processingfunction, and performs various signal processes such as an arithmeticprocess with respect to the pixel signal output from the columnprocessing unit 13. The data storage unit 19 temporarily stores datanecessary for the signal processing in the signal processing unit 18.

The signal processing unit 18 and the data storage unit 19 may bemounted on the same substrate (semiconductor substrate) as the CMOSimage sensor 10, or may be disposed on the substrate different from theCMOS image sensor 10. Each process of the signal processing unit 18 andthe data storage unit 19 may be executed as a process of an externalsignal processing unit, for example, a digital signal processor (DSP)circuit or software provided on the substrate different from the CMOSimage sensor 10.

In a case where the CMOS image sensor 10 is a rear surface irradiationtype CMOS image sensor, the CMOS image sensor may be configured as alaminated type CMOS image sensor obtained by bonding a semiconductorsubstrate including the pixel array unit 11 and a semiconductorsubstrate including a logic circuit to each other.

Pixel Array of Pixel Array Unit

Next, the pixel arrangement of the pixel array unit 11 will be describedwith reference to FIG. 2.

As shown in FIG. 2, a plurality of imaging pixels 31 shown as blacksquares are arranged in the pixel array unit 11 two-dimensionally in amatrix. The imaging pixels 31 are formed of R pixels, G pixels, and Bpixels, and these are regularly arranged along a Bayer array.

A plurality of phase difference detection pixels 32 shown as whitesquares are arranged in the pixel array unit 11 to be scattered in theplurality of imaging pixels 31 arranged two-dimensionally in a matrix.Specifically, the phase difference detection pixels 32 are substitutedwith some of the imaging pixels 31 in one predetermined row among thepixel rows in the pixel array unit 11, and thus are regularly arrangedin a specific pattern. The arrangement of the imaging pixels 31 and thephase difference detection pixels 32 in the pixel array unit 11 is notlimited thereto, and the pixels may be arranged in the other pattern.

Hereinafter, the embodiment of the imaging pixels 31 and the phasedifference detection pixels 32 in the pixel array unit 11 will bedescribed.

Configuration Example of Pixels of First Embodiment

FIG. 3 is a cross-sectional view showing a configuration example of thepixels of the CMOS image sensor 10 according to the first embodiment.FIG. 3 shows a cross-sectional view of the imaging pixels 31 and thephase difference detection pixels 32 of the CMOS image sensor 10.

As shown in FIG. 3, in the imaging pixel 31, a photoelectric conversionunit 52 which receives incident light and performs photoelectricconversion is formed on a semiconductor substrate 51, and an insulatinglayer 53 formed of SiO or the like is formed on the upper layer of thesemiconductor substrate 51. A plurality of wire layers 54 formed of Cuor Al are formed on the insulating layer 53.

A high refractive index film 55 formed of a high refractive indexmaterial having a photosensitive property is formed on the wire layers54. Examples of the high refractive index material having aphotosensitive property include TiO₂, ZrO₂, ZnO, and the like. Arefractive index of the high refractive index film 55 is set to a valuefrom 1.5 to 2.0. A color filter layer 56 having spectral characteristicscorresponding to each of the imaging pixels 31 is formed on the highrefractive index film 55, and a microlens 57 is formed on the colorfilter layer 56.

Meanwhile, the semiconductor substrate 51, the photoelectric conversionunit 52, the insulating layer 53, the wire layers 54, the color filterlayer 56, and the microlens 57 are also formed in the phase differencedetection pixel 32, in the same manner as the imaging pixel 31.

In the phase difference detection pixel 32, a part of the wire layer 54is formed as a light shielding film 54 a which shields some of the lightincident to the photoelectric conversion unit 52, to have an openinghaving a size which is substantially half of a light receiving area ofthe photoelectric conversion unit 52. A low refractive index film 58formed of a low refractive index material not having a photosensitiveproperty is formed between the wire layer 54 and the color filter layer56. As the low refractive index material not having a photosensitiveproperty, hollow silica is used, for example. The low refractive indexfilm 58 is formed so as to cover the high refractive index film 55 ofthe imaging pixel 31, and also functions as a flattening film when thecolor filter layer 56 is formed. A refractive index of the lowrefractive index film 58 is set to a value from 1.1 to 1.5.

In the phase difference detection pixel 32, a light attenuating filterfor attenuating incident light amount to the same extent as achieved bythe color filter layer 56 may be formed instead of the color filterlayer 56.

In the imaging pixel 31 and the phase difference detection pixel 32, themicrolenses 57 are formed in the same manner, that is, the microlenses57 are formed in the same shape and size, and have the same lightcondensing point, but the specific setting thereof can be performed byadjusting a refractive index or a film thickness of the high refractiveindex film 55 or the low refractive index film 58.

That is, the light condensing point of the microlens 57 in the imagingpixel 31 can be set on the light receiving surface of the photoelectricconversion unit 52 by the high refractive index film 55, and the lightcondensing point of the microlens 57 in the phase difference detectionpixel 32 can be set on the upper surface of the light shielding film 54a by the low refractive index film 58.

According to the configuration of the embodiment, since the highrefractive index film 55 is provided on the upper side of thephotoelectric conversion unit 52 in the imaging pixel 31 and the lowrefractive index film 58 is provided on the upper side of thephotoelectric conversion unit 52 in the phase difference detection pixel32, the light condensing point of the microlens 57 can be set on thelight receiving surface of the photoelectric conversion unit 52 in theimaging pixel 31, and the light condensing point of the microlens 57 canbe set on the upper surface of the light shielding film 54 a in thephase difference detection pixel 32. That is, it is possible to optimizethe sensitivity of the imaging pixel and the AF performance of the phasedifference detection pixel.

Since the microlenses 57 are formed in the same manner in the imagingpixel 31 and the phase difference detection pixel 32, it is possible toeasily perform a formation process of the microlens.

Flow of Pixel Formation

Next, a flow of the pixel formation of the embodiment will be describedwith reference to FIGS. 4 to 6C. FIG. 4 is a flowchart illustrating apixel formation process, and FIGS. 5A to 6C are cross-sectional viewsshowing a pixel formation step.

Hereinafter, as shown in FIG. 5A, a process after the wire layer 54 isformed will be described.

In Step S11, as shown in FIG. 5B, a high refractive index material 55 ahaving a photosensitive property is applied on the wire layer 54. A filmthickness of the high refractive index material 55 a is, for example,set to 400 nm, but is adjusted according to the light condensing pointof the microlens 57. A refractive index of the high refractive indexmaterial 55 a is, for example, set to 1.8, but is only necessary to behigher than a refractive index of a low refractive index material whichwill be described later, by a value equal to or greater than 0.1.

After the high refractive index material 55 a is applied, heating isperformed at 90° C. for 2 minutes, in order to remove a solvent of thehigh refractive index material 55 a and to harden the high refractiveindex material 55 a.

In Step S12, a pattern of the high refractive index material 55 a in anarea of the imaging pixel 31 is formed by photolithography. The patternof the high refractive index material 55 a is formed to have a sizesubstantially the same as the pixel size (size within ±15% of the pixelsize), for example. Accordingly, as shown in FIG. 5C, the highrefractive index film 55 is formed.

After the high refractive index film 55 is formed, heating is performedat 200° C. for 5 minutes in order to harden the high refractive indexfilm 55.

In Step S13, as shown in FIG. 6A, a low refractive index material 58 anot having a photosensitive property is applied so as to cover the highrefractive index film 55 by spin coating. A film thickness of the lowrefractive index material 58 a is, for example, set to 600 nm, but isadjusted according to the light condensing point of the microlens 57. Arefractive index of the low refractive index material 58 a is, forexample, set to 1.2, but is only necessary to be lower than therefractive index of the high refractive index material 55 a describedabove, by a value equal to or greater than 0.1.

Accordingly, the low refractive index film 58 is formed in the area ofthe phase difference detection pixel 32. Since the low refractive indexmaterial 58 a is applied so as to cover the high refractive index film55, the low refractive index material 58 a functions as a flatteningfilm with respect to the color filter layer 56 formed in a process in alater stage.

After the low refractive index material 58 a is applied, heating isperformed at 230° C. for 5 minutes, in order to remove a solvent of thelow refractive index material 58 a and to harden the low refractiveindex material 58 a.

In Step S14, as shown in FIG. 6B, the color filter layer 56 is formedfor each pixel.

In Step S15, as shown in FIG. 6C, the microlens 57 is formed in the samemanner in both of the imaging pixel 31 and the phase differencedetection pixel 32. A microlens material is formed as a film by spincoating, and the microlens material is etched back through aphotolithography step, and accordingly, the microlens 57 is formed.

By doing so, the imaging pixel 31 and the phase difference detectionpixel 32 are formed.

According to the processes described above, since the high refractiveindex film 55 is formed on the upper side of the photoelectricconversion unit 52 in the imaging pixel 31 and the low refractive indexfilm 58 is formed on the upper side of the photoelectric conversion unit52 in the phase difference detection pixel 32, the light condensingpoint of the microlens 57 can be set on the light receiving surface ofthe photoelectric conversion unit 52 in the imaging pixel 31, and thelight condensing point of the microlens 57 can be set on the uppersurface of the light shielding film 54 a in the phase differencedetection pixel 32. That is, it is possible to optimize the sensitivityof the imaging pixel and the AF performance of the phase differencedetection pixel.

In the processes described above, since the microlenses are formed inthe same manner, it is possible to suppress degradation of an image dueto variation of light condensing characteristics.

Other Configuration Example of Pixel

As described above, a cross-sectional shape of the high refractive indexfilm 55 of the imaging pixel 31 is set as a rectangle, but thecross-sectional shape of the high refractive index film 55 may be formedin a shape of a convex lens by photolithography, as shown in FIG. 7.

Configuration Example of Pixel of Second Embodiment

Next, a configuration example of pixels of a second embodiment will bedescribed with reference to FIG. 8.

The description of the portions of the imaging pixels 31 and the phasedifference detection pixels 32 shown in FIG. 8 and the imaging pixels 31and the phase difference detection pixels 32 shown in FIG. 3 which areformed in the same manner, will be omitted.

As shown in FIG. 8, a high refractive index film 71 formed of a highrefractive index material not having a photosensitive property is formedbetween the wire layer 54 and the color filter layer 56, in the imagingpixel 31. Examples of the high refractive index material not having aphotosensitive property include TiO₂, ZrO₂, ZnO, and the like. The highrefractive index film 71 is formed so as to cover a low refractive indexfilm 72 of the phase difference detection pixel 32, and also functionsas a flattening film when the color filter layer 56 is formed.

A low refractive index film 72 formed of a low refractive index materialhaving a photosensitive property is formed between the wire layer 54 andthe color filter layer 56, in the phase difference detection pixel 32.As the low refractive index material having a photosensitive property,hollow silica is used, for example. In FIG. 8, the low refractive indexfilm 72 is formed so that the cross-sectional shape thereof is formed ina shape of a convex lens, but may be formed so that the cross-sectionalshape thereof is set as a rectangle.

Also, in the embodiment, in the imaging pixel 31 and the phasedifference detection pixel 32, the microlenses 57 are formed in the samemanner, that is, the microlenses 57 are formed in the same shape andsize, and have the same light condensing point, but the specific settingthereof can be performed by adjusting a refractive index or a filmthickness of the high refractive index film 71 or the low refractiveindex film 72.

That is, the light condensing point of the microlens 57 in the imagingpixel 31 can be set on the light receiving surface of the photoelectricconversion unit 52 by the high refractive index film 71, and the lightcondensing point of the microlens 57 in the phase difference detectionpixel 32 can be set on the upper surface of the light shielding film 54a by the low refractive index film 72.

According to the configuration of the embodiment, since the highrefractive index film 71 is provided on the upper side of thephotoelectric conversion unit 52 in the imaging pixel 31 and the lowrefractive index film 72 is provided on the upper side of thephotoelectric conversion unit 52 in the phase difference detection pixel32, the light condensing point of the microlens 57 can be set on thelight receiving surface of the photoelectric conversion unit 52 in theimaging pixel 31, and the light condensing point of the microlens 57 canbe set on the upper surface of the light shielding film 54 a in thephase difference detection pixel 32. That is, it is possible to optimizethe sensitivity of the imaging pixel and the AF performance of the phasedifference detection pixel.

Flow of Pixel Formation

Next, a flow of the pixel formation of the embodiment will be describedwith reference to FIGS. 9 to 11C. FIG. 9 is a flowchart illustrating apixel formation process, and FIGS. 10A to 11C are cross-sectional viewsshowing a pixel formation step.

Also, hereinafter, as shown in FIG. 10A, a process after the wire layer54 is formed will be described.

In Step S31, as shown in FIG. 10B, a low refractive index material 72 ahaving a photosensitive property is applied on the wire layer 54. A filmthickness of the low refractive index material 72 a is, for example, setto 400 nm, but is adjusted according to the light condensing point ofthe microlens 57. A refractive index of the low refractive indexmaterial 72 a is, for example, set to 1.4, but is only necessary to belower than a refractive index of a high refractive index material whichwill be described later, by a value equal to or greater than 0.1.

After the low refractive index material 72 a is applied, heating isperformed at 90° C. for 2 minutes, in order to remove a solvent of thelow refractive index material 72 a and to harden the low refractiveindex material 72 a.

In Step S32, as shown in FIG. 10C, a pattern of the low refractive indexmaterial 72 a in the area of the phase difference detection pixel 32 isformed by photolithography. The pattern of the high refractive indexmaterial 72 a is formed to have a size substantially the same as thepixel size (size within ±15% of the pixel size), for example.

In Step S33, heating is performed and the low refractive index material72 a is subjected to reflow, and accordingly, the low refractive indexmaterial 72 a is formed in a lens shape. Herein, heating is performed ina stepwise manner, by performing heating at 140° C. for 2 minutes andheating at 175° C. for 2 minutes, for example. Accordingly, as shown inFIG. 10D, the low refractive index film 72 having a cross-sectionalshape of a convex lens shape is formed.

After the lens shape is formed, heating is performed at 250° C. whileemitting ultraviolet (UV) light, in order to decompose a photosensitivematerial included in the low refractive index material 72 a and toharden the low refractive index material 72 a.

In Step S34, as shown in FIG. 11A, a high refractive index material 71 anot having a photosensitive property is applied so as to cover the lowrefractive index film 72 by spin coating. A film thickness of the highrefractive index material 71 a is, for example, set to 600 nm, but isadjusted according to the light condensing point of the microlens 57. Arefractive index of the high refractive index material 71 a is, forexample, set to 1.8, but is only necessary to be higher than therefractive index of the low refractive index material 72 a describedabove, by a value equal to or greater than 0.1.

Accordingly, the high refractive index film 71 is formed in the area ofthe imaging pixel 31. Since the high refractive index material 71 a isapplied so as to cover the low refractive index film 72, the highrefractive index material 71 a functions as a flattening film withrespect to the color filter layer 56 formed in a process in a laterstage.

After the high refractive index material 71 a is applied, heating isperformed at 230° C. for 5 minutes, in order to remove a solvent of thehigh refractive index material 71 a and to harden the high refractiveindex material 71 a.

In Step S35, as shown in FIG. 11B, the color filter layer 56 is formedfor each pixel.

In Step S36, as shown in FIG. 11C, the microlens 57 is formed in thesame manner in both of the imaging pixel 31 and the phase differencedetection pixel 32, in the same manner as in the first embodiment.

By doing so, the imaging pixel 31 and the phase difference detectionpixel 32 are formed.

According to the processes described above, since the high refractiveindex film 71 is formed on the upper side of the photoelectricconversion unit 52 in the imaging pixel 31 and the low refractive indexfilm 72 is formed on the upper side of the photoelectric conversion unit52 in the phase difference detection pixel 32, the light condensingpoint of the microlens 57 can be set on the light receiving surface ofthe photoelectric conversion unit 52 in the imaging pixel 31, and thelight condensing point of the microlens 57 can be set on the uppersurface of the light shielding film 54 a in the phase differencedetection pixel 32. That is, it is possible to optimize the sensitivityof the imaging pixel and the AF performance of the phase differencedetection pixel.

Also, in the processes described above, since the microlenses are formedin the same manner, it is possible to suppress degradation of an imagedue to variation of light condensing characteristics.

Configuration Example of Pixel of Third Embodiment

Next, a configuration example of pixels of a third embodiment will bedescribed with reference to FIG. 12.

The description of the portions of the imaging pixels 31 and the phasedifference detection pixels 32 shown in FIG. 12 and the imaging pixels31 and the phase difference detection pixels 32 shown in FIG. 3 whichare formed in the same manner, will be omitted.

As shown in FIG. 12, a high refractive index film 81 formed of a highrefractive index material having a photosensitive property is formedbetween the wire layer 54 and the color filter layer 56, in the imagingpixel 31. Examples of the high refractive index material having aphotosensitive property include TiO₂, ZrO₂, ZnO, and the like.

A low refractive index film 82 formed of a low refractive index materialhaving a photosensitive property is formed between the wire layer 54 andthe color filter layer 56, in the phase difference detection pixel 32.As the low refractive index material having a photosensitive property,hollow silica is used, for example.

Also, in the embodiment, in the imaging pixel 31 and the phasedifference detection pixel 32, the microlenses 57 are formed in the samemanner, that is, the microlenses 57 are formed in the same shape andsize, and have the same light condensing point, but the specific settingthereof can be performed by adjusting a refractive index or a filmthickness of the high refractive index film 81 or the low refractiveindex film 82.

That is, the light condensing point of the microlens 57 in the imagingpixel 31 can be set on the light receiving surface of the photoelectricconversion unit 52 by the high refractive index film 81, and the lightcondensing point of the microlens 57 in the phase difference detectionpixel 32 can be set on the upper surface of the light shielding film 54a by the low refractive index film 82.

According to the configuration of the embodiment, since the highrefractive index film 81 is provided on the upper side of thephotoelectric conversion unit 52 in the imaging pixel 31 and the lowrefractive index film 82 is provided on the upper side of thephotoelectric conversion unit 52 in the phase difference detection pixel32, the light condensing point of the microlens 57 can be set on thelight receiving surface of the photoelectric conversion unit 52 in theimaging pixel 31, and the light condensing point of the microlens 57 canbe set on the upper surface of the light shielding film 54 a in thephase difference detection pixel 32. That is, it is possible to optimizethe sensitivity of the imaging pixel and the AF performance of the phasedifference detection pixel.

Flow of Pixel Formation

Next, a flow of the pixel formation of the embodiment will be describedwith reference to FIGS. 13 to 15C. FIG. 13 is a flowchart illustrating apixel formation process, and FIGS. 14A to 15C are cross-sectional viewsshowing a pixel formation step.

Also, hereinafter, as shown in FIG. 14A, a process after the wire layer54 is formed will be described.

In Step S51, as shown in FIG. 14B, a low refractive index material 82 ahaving a photosensitive property is applied onto the wire layer 54 byspin coating. A film thickness of the low refractive index material 82 ais, for example, set to 400 nm, but is adjusted according to the lightcondensing point of the microlens 57. A refractive index of the lowrefractive index material 82 a is, for example, set to 1.4, but is onlynecessary to be lower than a refractive index of a high refractive indexmaterial which will be described later, by a value equal to or greaterthan 0.1. The low refractive index material 82 a is a negative typeresist or may be a positive type resist.

In Step S52, a pattern of the low refractive index material 82 a in thearea of the phase difference detection pixel 32 is formed by performinglight exposure and development by photolithography. Accordingly, asshown in FIG. 14C, the low refractive index film 82 is formed.

Herein, after the development, heating is performed at 200° C. for 10minutes, in order to remove a solvent of the low refractive indexmaterial 82 a and to harden the low refractive index material 82 a.

In Step S53, as shown in FIG. 14D, a high refractive index material 81 ahaving a photosensitive property is applied so as to cover the lowrefractive index film 82 by spin coating. A film thickness of the highrefractive index material 81 a is, for example, set to 400 nm, but isadjusted according to the light condensing point of the microlens 57. Arefractive index of the high refractive index material 81 a is, forexample, set to 1.8, but is only necessary to be higher than therefractive index of the low refractive index material 82 a describedabove, by a value equal to or greater than 0.1. The high refractiveindex material 81 a is a negative type resist or may be a positive typeresist.

In Step S54, a pattern of the high refractive index material 81 a in thearea of the imaging pixel 31 is formed by performing light exposure anddevelopment by photolithography. Accordingly, as shown in FIG. 15A, ahigh refractive index film 81 is formed.

Herein, after the development, heating is performed at 200° C. for 10minutes, in order to remove a solvent of the high refractive indexmaterial 81 a and to harden the high refractive index material 81 a.

In Step S55, as shown in FIG. 15B, the color filter layer 56 is formedfor each pixel.

In Step S56, as shown in FIG. 15C, the microlens 57 is formed in thesame manner in both of the imaging pixel 31 and the phase differencedetection pixel 32, in the same manner as in the first embodiment.

By doing so, the imaging pixel 31 and the phase difference detectionpixel 32 are formed.

According to the processes described above, since the high refractiveindex film 81 is formed on the upper side of the photoelectricconversion unit 52 in the imaging pixel 31 and the low refractive indexfilm 82 is formed on the upper side of the photoelectric conversion unit52 in the phase difference detection pixel 32, the light condensingpoint of the microlens 57 can be set on the light receiving surface ofthe photoelectric conversion unit 52 in the imaging pixel 31, and thelight condensing point of the microlens 57 can be set on the uppersurface of the light shielding film 54 a in the phase differencedetection pixel 32. That is, it is possible to optimize the sensitivityof the imaging pixel and the AF performance of the phase differencedetection pixel.

Also, in the processes described above, since the microlenses are formedin the same manner, it is possible to suppress degradation of an imagedue to variation of light condensing characteristics.

In the processes described above, the high refractive index film 81 isformed after the low refractive index film 82 is formed, but the lowrefractive index film 82 may be formed after the high refractive indexfilm 81 is formed.

Other Example of Flow of Pixel Formation

Herein, a flow of the pixel formation of the embodiment will bedescribed with reference to FIGS. 16 to 18C. FIG. 16 is a flowchartillustrating a pixel formation process, and FIGS. 17A to 18C arecross-sectional views showing a pixel formation step.

Also, hereinafter, as shown in FIG. 17A, a process after the wire layer54 is formed will be described.

In Step S71, as shown in FIG. 17B, the high refractive index material 81a having a photosensitive property is applied onto the wire layer 54 byspin coating. The film thickness of the high refractive index material81 a is, for example, set to 500 nm, but is adjusted according to thelight condensing point of the microlens 57. The refractive index of thehigh refractive index material 81 a is, for example, set to 1.8, but isonly necessary to be higher than a refractive index of a low refractiveindex material which will be described later, by a value equal to orgreater than 0.1. The high refractive index material 81 a is a negativetype resist or may be a positive type resist.

In Step S72, a pattern of the high refractive index material 81 a in thearea of the imaging pixel 31 is formed by performing light exposure anddevelopment by photolithography. Accordingly, as shown in FIG. 17C, thehigh refractive index film 81 is formed.

Herein, after the development, heating is performed at 200° C. for 10minutes, in order to remove a solvent of the high refractive indexmaterial 81 a and to harden the high refractive index material 81 a.

In Step S73, as shown in FIG. 17D, the low refractive index material 82a having a photosensitive property is applied so as to cover the highrefractive index film 81 by spin coating. The film thickness of the lowrefractive index material 82 a is, for example, set to 400 nm, but isadjusted according to the light condensing point of the microlens 57.The refractive index of the low refractive index material 82 a is, forexample, set to 1.2, but is only necessary to be lower than therefractive index of the high refractive index material 81 a describedabove, by a value equal to or greater than 0.1. The low refractive indexmaterial 82 a is a negative type resist or may be a positive typeresist.

In Step S74, a pattern of the low refractive index material 82 a in thearea of the phase difference detection pixel 32 is formed by performinglight exposure and development by photolithography. Accordingly, asshown in FIG. 18A, the low refractive index film 82 is formed.

Herein, after the development, heating is performed at 200° C. for 10minutes, in order to remove a solvent of the low refractive indexmaterial 82 a and to harden the low refractive index material 82 a.

In Step S75, as shown in FIG. 18B, the color filter layer 56 is formedfor each pixel.

In Step S76, as shown in FIG. 18C, the microlens 57 is formed in thesame manner in both of the imaging pixel 31 and the phase differencedetection pixel 32, in the same manner as in the first embodiment.

By doing so, the imaging pixel 31 and the phase difference detectionpixel 32 are formed.

Configuration Example of Pixels of Fourth Embodiment

Next, a configuration example of pixels of a fourth embodiment will bedescribed with reference to FIG. 19.

The description of the portions of the imaging pixels 31 and the phasedifference detection pixels 32 shown in FIG. 19 and the imaging pixels31 and the phase difference detection pixels 32 shown in FIG. 3 whichare formed in the same manner, will be omitted.

As shown in FIG. 19, a high refractive index film 91 formed of a highrefractive index material not having a photosensitive property is formedbetween the wire layer 54 and the color filter layer 56, in the imagingpixel 31. Examples of the high refractive index material not having aphotosensitive property include TiO₂, ZrO₂, ZnO, and the like.

A low refractive index film 92 formed of a low refractive index materialhaving a photosensitive property is formed between the wire layer 54 andthe color filter layer 56, in the phase difference detection pixel 32.As the low refractive index material having a photosensitive property,hollow silica is used, for example.

Also, in the embodiment, in the imaging pixel 31 and the phasedifference detection pixel 32, the microlenses 57 are formed in the samemanner, that is, the microlenses 57 are formed in the same shape andsize, and have the same light condensing point, but the specific settingthereof can be performed by adjusting a refractive index or a filmthickness of the high refractive index film 91 or the low refractiveindex film 92.

That is, the light condensing point of the microlens 57 in the imagingpixel 31 can be set on the light receiving surface of the photoelectricconversion unit 52 by the high refractive index film 91, and the lightcondensing point of the microlens 57 in the phase difference detectionpixel 32 can be set on the upper surface of the light shielding film 54a by the low refractive index film 92.

According to the configuration of the embodiment, since the highrefractive index film 91 is provided on the upper side of thephotoelectric conversion unit 52 in the imaging pixel 31 and the lowrefractive index film 92 is provided on the upper side of thephotoelectric conversion unit 52 in the phase difference detection pixel32, the light condensing point of the microlens 57 can be set on thelight receiving surface of the photoelectric conversion unit 52 in theimaging pixel 31, and the light condensing point of the microlens 57 canbe set on the upper surface of the light shielding film 54 a in thephase difference detection pixel 32. That is, it is possible to optimizethe sensitivity of the imaging pixel and the AF performance of the phasedifference detection pixel.

Flow of Pixel Formation

Next, a flow of the pixel formation of the embodiment will be describedwith reference to FIGS. 20 to 22D. FIG. 20 is a flowchart illustrating apixel formation process, and FIGS. 21A to 22D are cross-sectional viewsshowing a pixel formation step.

Also, hereinafter, as shown in FIG. 21A, a process after the wire layer54 is formed will be described.

In Step S91, as shown in FIG. 21B, a high refractive index material 91 anot having a photosensitive property is applied onto the wire layer 54by spin coating. A film thickness of the high refractive index material91 a is, for example, set to 500 nm, but is adjusted according to thelight condensing point of the microlens 57. A refractive index of thehigh refractive index material 91 a is, for example, set to 1.8, but isonly necessary to be higher than a refractive index of a low refractiveindex material which will be described later, by a value equal to orgreater than 0.1.

After the high refractive index material 91 a is applied, heating isperformed at 200° C. for 10 minutes, in order to remove a solvent of thehigh refractive index material 91 a and to harden the high refractiveindex material 91 a.

In Step S92, as shown in FIG. 21C, a photoresist 101 is formed in anarea on the high refractive index material 91 a other than the phasedifference detection pixel 32 (that is, area of the imaging pixel 31).

In Step S93, the high refractive index material 91 a in the area of thephase difference detection pixel 32 is dry-etched. Accordingly, as shownin FIG. 21D, the high refractive index film 91 is formed.

In Step S94, as shown in FIG. 22A, a low refractive index material 92 ahaving a photosensitive property is applied so as to cover the highrefractive index film 91 by spin coating. A film thickness of the lowrefractive index material 92 a is, for example, set to 400 nm, but isadjusted according to the light condensing point of the microlens 57. Arefractive index of the low refractive index material 92 a is, forexample, set to 1.4, but is only necessary to be lower than therefractive index of the high refractive index material 91 a describedabove, by a value equal to or greater than 0.1. The low refractive indexmaterial 92 a is a negative type resist or may be a positive typeresist.

In Step S95, a pattern of the low refractive index material 92 a in thearea of the phase difference detection pixel 32 is formed by performinglight exposure and development by photolithography. Accordingly, asshown in FIG. 22B, the low refractive index film 92 is formed.

Herein, i-ray exposure is only performed in the area of the phasedifference detection pixel 32 with an exposure amount of 5000 J/m2 and afocus offset of 0 μm, and after the development, heating is performed at200° C. for 10 minutes, in order to remove a solvent of the lowrefractive index material 92 a and to harden the low refractive indexmaterial 92 a.

In Step S96, as shown in FIG. 22C, the color filter layer 56 is formedfor each pixel.

In Step S97, as shown in FIG. 22D, the microlens 57 is formed in thesame manner in both of the imaging pixel 31 and the phase differencedetection pixel 32, in the same manner as in the first embodiment.

According to the processes described above, since the high refractiveindex film 91 is formed on the upper side of the photoelectricconversion unit 52 in the imaging pixel 31 and the low refractive indexfilm 92 is formed on the upper side of the photoelectric conversion unit52 in the phase difference detection pixel 32, the light condensingpoint of the microlens 57 can be set on the light receiving surface ofthe photoelectric conversion unit 52 in the imaging pixel 31, and thelight condensing point of the microlens 57 can be set on the uppersurface of the light shielding film 54 a in the phase differencedetection pixel 32. That is, it is possible to optimize the sensitivityof the imaging pixel and the AF performance of the phase differencedetection pixel.

As described above, the configuration in which the present technology isapplied to the surface irradiation type CMOS image sensor has beendescribed, but hereinafter, a configuration in which the presenttechnology is applied to the rear surface irradiation type CMOS imagesensor will be described.

Configuration Example of Pixels of Fifth Embodiment

FIG. 23 is a cross-sectional view showing a configuration example of thepixels of the rear surface irradiation type CMOS image sensor 10according to a fifth embodiment. FIG. 23 shows a cross-sectional view ofthe imaging pixels 31 and the phase difference detection pixels 32 ofthe rear surface irradiation type CMOS image sensor 10.

As shown in FIG. 23, in the imaging pixel 31, a photoelectric conversionunit 152 is formed on a semiconductor substrate 151 and an insulatinglayer 153 is formed on the upper layer of the semiconductor substrate151.

A high refractive index film 154 formed of a high refractive indexmaterial is formed on the insulating layer 153. The high refractiveindex film 154 may be formed of a high refractive index material havinga photosensitive property or may be formed of a high refractive indexmaterial not having a photosensitive property. A color filter layer 155is formed on the high refractive index film 154, and a microlens 156 isformed on the color filter layer 155.

Meanwhile, the semiconductor substrate 151, the photoelectric conversionunit 152, the insulating layer 153, the color filter layer 155, and themicrolens 156 are also formed in the phase difference detection pixel32, in the same manner as the imaging pixel 31.

In the phase difference detection pixel 32, a light shielding film 157is formed on the insulating layer 153 to have an opening having a sizewhich is substantially half of a light receiving area of thephotoelectric conversion unit 152. A low refractive index film 158formed of a low refractive index material is formed on a lower portionof the color filter layer 155. The low refractive index film 158 may bea low refractive index material having a photosensitive property or maybe formed of a low refractive index material not having a photosensitiveproperty.

In the phase difference detection pixel 32, a light attenuating filterfor attenuating incident light amount to the same extent as achieved bythe color filter layer 155 may be formed instead of the color filterlayer 155.

In the rear surface irradiation type CMOS image sensor 10, a wire layer159 is formed on a surface opposite to the surface where the microlens156 is formed.

Also, in the embodiment, in the imaging pixel 31 and the phasedifference detection pixel 32, the microlenses 156 are formed in thesame manner, that is, the microlenses 57 are formed in the same shapeand size, and have the same light condensing point, but the specificsetting thereof can be performed by adjusting a refractive index or afilm thickness of the high refractive index film 154 or the lowrefractive index film 158.

That is, the light condensing point of the microlens 156 in the imagingpixel 31 can be set on the light receiving surface of the photoelectricconversion unit 152 by the high refractive index film 154, and the lightcondensing point of the microlens 156 in the phase difference detectionpixel 32 can be set on the upper surface of the light shielding film 157by the low refractive index film 158.

According to the configuration of the embodiment, since the highrefractive index film 154 is provided on the upper side of thephotoelectric conversion unit 152 in the imaging pixel 31 and the lowrefractive index film 158 is provided on the upper side of thephotoelectric conversion unit 152 in the phase difference detectionpixel 32, the light condensing point of the microlens 156 can be set onthe light receiving surface of the photoelectric conversion unit 152 inthe imaging pixel 31, and the light condensing point of the microlens156 can be set on the upper surface of the light shielding film 157 inthe phase difference detection pixel 32. That is, it is possible tooptimize the sensitivity of the imaging pixel and the AF performance ofthe phase difference detection pixel.

In the configuration described above, since the high refractive indexfilm is provided on the upper side of the photoelectric conversion unitin the imaging pixel and the low refractive index film is provided onthe upper side of the photoelectric conversion unit in the phasedifference detection pixel, the sensitivity of the phase differencedetection pixel is decreased while optimizing the sensitivity of theimaging pixel, but these can also be realized by the otherconfiguration.

Hereinafter, as shown in FIG. 24, a configuration in which some of Gpixels 31G among R pixels 31R, G pixels 31G, and B pixels 31B as theimaging pixels 31 regularly arranged along a Bayer array are substitutedwith the phase difference detection pixels 32, will be described.

Configuration Example of Pixels of Sixth Embodiment

FIG. 25 is a cross-sectional view showing a configuration example of thepixels of the CMOS image sensor 10 according to the sixth embodiment.FIG. 25 shows a cross-sectional view of the G pixel 31G among theimaging pixels 31 of the CMOS image sensor 10 and the phase differencedetection pixel 32.

As shown in FIG. 25, in the imaging pixel 31, a photoelectric conversionunit 252 which receives incident light and performs photoelectricconversion is formed on a semiconductor substrate 251, and an insulatinglayer 253 formed of SiO or the like is formed on the upper layer of thesemiconductor substrate 251. A plurality of wire layers 254 formed of Cuor Al are formed on the insulating layer 253.

A flattening film 255 is formed on the wire layer 254, and a green colorfilter 256G having spectral characteristics corresponding to the G pixel31G is formed on the flattening film 255. A microlens 257 is formed onthe color filter 256G. In the example of FIG. 25, since a red colorfilter 256R is formed on the same layer as the color filter 256G, the Rpixel 31R is formed adjacent to the G pixel 31G.

Meanwhile, the semiconductor substrate 251, the photoelectric conversionunit 252, the insulating layer 253, the wire layers 254, and themicrolens 257 are also formed in the phase difference detection pixel32, in the same manner as the G pixel 31G.

In the phase difference detection pixel 32, a part of the wire layer 254is formed as a light shielding film 254 a which shields some of thelight incident to the photoelectric conversion unit 252, to have anopening having a size which is substantially half of a light receivingarea of the photoelectric conversion unit 252. A color filter 256G′ isformed on the same layer as the color filter 256G. The color filter256G′ is formed to have a film thickness smaller than that of the colorfilter 256G.

In the related art, for example, in the solid-state imaging device inwhich some of G pixels are substituted with the phase differencedetection pixels, the film thickness of the green color filter isdetermined so as to optimize the sensitivity of the G pixel (imagingpixel). However, in the phase difference detection pixel, thesensitivity thereof is set to be lower than the sensitivity of the Gpixel, by the light shielding film.

According to the configuration of the embodiment, since the color filter256G′ included in the phase difference detection pixel 32 is formed soas to have the film thickness to be smaller than the film thickness ofthe color filter 256G included in the G pixel 31G, it is possible tooptimize the sensitivity of the imaging pixel and to suppress a decreasein the sensitivity of the phase difference detection pixel. That is, itis possible to optimize the sensitivity of the imaging pixel and the AFperformance of the phase difference detection pixel.

In the imaging pixel 31 and the phase difference detection pixel 32, ashape or a size of the microlens 257 may be determined depending on thefilm thickness of the color filter 256G or the color filter 256G′.

Flow of Pixel Formation

Next, a flow of the pixel formation of the embodiment will be describedwith reference to FIGS. 26 to 28C. FIG. 26 is a flowchart illustrating apixel formation process, and FIGS. 27A to 28C are cross-sectional viewsshowing a pixel formation step.

Hereinafter, a process after the wire layer 254 is formed will bedescribed.

In Step S111, as shown in FIG. 27A, a flattening film 255 is formed onthe wire layer 254.

In Step S112, as shown in FIG. 27B, a green color filter (CF) material256 g is applied onto the flattening film 255. Hereinafter, a negativephotoresist is used as the CF material 256 g. A positive photoresist canbe used as the CF material 256 g, but in this case, an exposure patternof a reticle used for light exposure is a reversed exposure pattern of areticle which will be described later, and it is also necessary to setcounter light exposure conditions.

In Step S113, as shown in FIG. 27C, by using a reticle 271, the CFmaterial 256 g corresponding to the G pixel 31G is exposed to the lightwith the predetermined light exposure conditions (exposure amount,exposure illuminance, and the like). As shown in FIG. 29, the reticle271 has an exposure pattern of exposing only the pixel area in which theG pixels 31G are formed (white parts in the drawing). Accordingly, asshown in FIG. 27C, an area H1 of the CF material 256 g is only exposedto the light.

Next, in Step S114, as shown in FIG. 27D, by using a reticle 272, the CFmaterial 256 g corresponding to the phase difference detection pixel 32is exposed to the light with the light exposure conditions differentfrom the light exposure conditions in Step S113, specifically, with asmaller exposure amount, a lower exposure illuminance, and the like. Asshown in FIG. 30, the reticle 272 has an exposure pattern of exposingonly the pixel area in which the phase difference detection pixel 32 isformed (white parts in the drawing). Accordingly, as shown in FIG. 27D,an area H2 of the CF material 256 g is only exposed to the light.

The process in Step S113 and the process in Step S114 are consecutivelyperformed without interruption.

In Step S115, the CF material 256 g is developed. Specifically, an areaof the CF material 256 g not exposed in Step S113 or Step S114 isremoved by a developer. At that time, among the area of the CF material256 g exposed in Step S113 or Step S114, a film thickness of the area H2is set to be smaller than the film thickness of the area H1.

By doing so, as shown in FIG. 28A, the color filter 256G′ included inthe phase difference detection pixel 32 is formed to have a filmthickness smaller than the film thickness of the color filter 256Gincluded in the G pixel 31G.

In Step S116, a red CF material 256 r (not shown) is applied on theflattening film 255.

In Step S117, although not shown, by using a reticle having an exposurepattern of exposing only the pixel area in which the R pixels 31R areformed, the CF material 256 r corresponding to the R pixel 31R isexposed to the light with the predetermined light exposure conditions.

In Step S118, the CF material 256 r is developed. Accordingly, as shownin FIG. 28B, the color filter 256R included in the R pixel 31R isformed. The film thickness of the color filter 256R is set to be thesame as the film thickness of the color filter 256G included in the Gpixel 31G.

In Step S119, a blue CF material 256 b (not shown) is applied on theflattening film 255.

In Step S120, although not shown, by using a reticle having an exposurepattern of exposing only the pixel area in which the B pixels 31B areformed, the CF material 256 b corresponding to the B pixel 31B isexposed to the light with the predetermined light exposure conditions.

In Step S121, the CF material 256 b is developed. Accordingly, a colorfilter 256B (not shown) included in the B pixel 31B is formed. The filmthickness of the color filter 256B is also set to be the same as thefilm thickness of the color filter 256G included in the G pixel 31G.

By doing so, after the color filter is formed for each pixel, themicrolens 257 is formed for each pixel in Step S122, as shown in FIG.28C. A microlens material is formed as a film by spin coating, and themicrolens material is etched back through a photolithography step, andaccordingly, the microlens 257 is formed.

By doing so, the imaging pixel 31 and the phase difference detectionpixel 32 are formed.

According to the processes described above, since the color filter 256G′included in the phase difference detection pixel 32 is formed so as tohave the film thickness to be smaller than the film thickness of thecolor filter 256G included in the G pixel 31G, it is possible tooptimize the sensitivity of the imaging pixel and to suppress a decreasein the sensitivity of the phase difference detection pixel. That is, itis possible to optimize the sensitivity of the imaging pixel and the AFperformance of the phase difference detection pixel.

In addition, since the process in Step S113 and the process in Step S114are consecutively performed without interruption, when the flow of thecoating, the exposure, and the development of the CF material is set asone step, it is possible to form the imaging pixel 31 and the phasedifference detection pixel 32 in three steps which are the same as thegeneral pixel formation process in which the R pixels, the G pixels, andthe B pixels are arranged in a Bayer array, and it is possible to avoidan increase of the number of steps.

In the processes described above, the exposure of the pixel area inwhich the G pixel 31G is formed and the exposure of the pixel area inwhich the phase difference detection pixels 32 is formed are separatelyperformed, but these may be collectively performed.

Other Example of Flow of Pixel Formation

Herein, the other example of a flow of the pixel formation of theembodiment will be described with reference to FIGS. 31 to 32D. FIG. 31is a flowchart illustrating a pixel formation process, and FIGS. 32A to32D are cross-sectional views showing a pixel formation step.

Also, hereinafter, a process after the wire layer 254 is formed will bedescribed.

In Step S131, as shown in FIG. 32A, the flattening film 255 is formed onthe wire layer 254.

In Step S132, as shown in FIG. 32B, the CF material 256 g is appliedonto the flattening film 255.

In Step S133, as shown in FIG. 32C, by using a gray scale mask 281, theCF material 256 g corresponding to the G pixel 31G and the phasedifference detection pixel 32 is exposed to the light with thepredetermined light exposure conditions (exposure amount, exposureilluminance, and the like). As shown in FIG. 33, the gray scale mask 281has a first exposure pattern of exposing the pixel area in which the Gpixels 31G are formed (white parts in the drawing), and a secondexposure pattern of exposing the pixel area in which the phasedifference detection pixels 32 are formed (light gray parts in thedrawing). In the gray scale mask 281, the light transmittance of thesecond exposure pattern is set to be different from light transmittanceof the first exposure pattern (specifically, to be lower than the lighttransmittance of the first exposure pattern). Accordingly, as shown inFIG. 32C, the area H2 of the CF material 256 g is exposed to the lightwith smaller exposure amount and lower exposure illuminance than thoseof the area H1.

In Step S134, the CF material 256 g is developed. Specifically, the areaof the CF material 256 g not exposed in Step S113 is removed by adeveloper. At that time, among the area of the CF material 256 g exposedin Step S113, the film thickness of the area H2 is set to be smallerthan the film thickness of the area H1.

By doing so, as shown in FIG. 32D, the color filter 256G′ included inthe phase difference detection pixel 32 is formed to have a filmthickness smaller than the film thickness of the color filter 256Gincluded in the G pixel 31G.

The processes in Step S135 and the subsequent steps are the same as theprocesses in Step S116 and the subsequent steps in the flowchart of FIG.26, and therefore the description thereof will be omitted.

Also, according to the processes described above, since the color filter256G′ included in the phase difference detection pixel 32 is formed soas to have the film thickness to be smaller than the film thickness ofthe color filter 256G included in the G pixel 31G, it is possible tooptimize the sensitivity of the imaging pixel and to suppress a decreasein the sensitivity of the phase difference detection pixel. That is, itis possible to optimize the sensitivity of the imaging pixel and the AFperformance of the phase difference detection pixel.

Also, in the processes described above, it is possible to form theimaging pixel 31 and the phase difference detection pixel 32 in threesteps which are the same as the general pixel formation process in whichthe R pixels, the G pixels, and the B pixels are arranged in a Bayerarray, and it is possible to avoid an increase of the number of steps.

As described above, the configuration in which the present technology isapplied to the surface irradiation type CMOS image sensor has beendescribed, but hereinafter, a configuration in which the presenttechnology is applied to the rear surface irradiation type CMOS imagesensor will be described.

Configuration Example of Pixels of Seventh Embodiment

FIG. 34 is a cross-sectional view showing a configuration example of thepixels of the rear surface irradiation type CMOS image sensor 10according to a seventh embodiment. FIG. 34 shows a cross-sectional viewof the G pixel 31G among the imaging pixels 31, and the phase differencedetection pixels 32 of the rear surface irradiation type CMOS imagesensor 10.

As shown in FIG. 34, in the G pixel 31G, a photoelectric conversion unit352 is formed on a semiconductor substrate 351 and an insulating layer353 is formed on the upper layer of the semiconductor substrate 351.

A flattening film 354 is formed on the insulating layer 353, and a greencolor filter 355G having spectral characteristics corresponding to the Gpixel 31G is formed on the flattening film 354. A microlens 356 isformed on the color filter 355G. Also, in the example of FIG. 34, sincea red color filter 355R is formed on the same layer as the color filter355G, the R pixel 31R is formed adjacent to the G pixel 31G.

Meanwhile, the semiconductor substrate 351, the photoelectric conversionunit 352, the insulating layer 353, and the microlens 356 are alsoformed in the phase difference detection pixel 32, in the same manner asthe imaging pixel 31.

In the phase difference detection pixel 32, a light shielding film 357is formed on the insulating layer 353 to have an opening having a sizewhich is substantially half of a light receiving area of thephotoelectric conversion unit 352. A color filter 355G′ is formed on thesame layer as the color filter 355G. The color filter 355G′ is formed tohave a film thickness smaller than that of the color filter 355G.

In the rear surface irradiation type CMOS image sensor 10, a wire layer358 is formed on a surface opposite to the surface where the microlens356 is formed.

Also, in the embodiment, since the color filter 355G′ included in thephase difference detection pixel 32 is formed so as to have the filmthickness to be smaller than the film thickness of the color filter 355Gincluded in the G pixel 31G, it is possible to optimize the sensitivityof the imaging pixel and to suppress a decrease in the sensitivity ofthe phase difference detection pixel. That is, it is possible tooptimize the sensitivity of the imaging pixel and the AF performance ofthe phase difference detection pixel.

Modification Example

As described above, the configuration in which some of the G pixels 31Gamong the R pixels 31R, the G pixels 31G, and the B pixels 31B as theimaging pixels 31 arranged along a Bayer array are substituted with thephase difference detection pixels 32, has been described, but some ofthe R pixels 31R or the B pixels 31B may be substituted with the phasedifference detection pixels 32.

In this case, a color filter included in the phase difference detectionpixel 32 is formed so as to have a film thickness to be smaller than afilm thickness of a color filter 256R included in the R pixel 31R, or acolor filter 256B included in the B pixel 31B.

As shown in FIG. 35, when white pixels (W pixels) 31W are arranged alonga Bayer array as the imaging pixels 31, instead of the R pixels 31R, theG pixels 31G, and the B pixels 31B, some of the W pixels 31W may besubstituted with the phase difference detection pixels 32. Since a colorfilter included in the W pixel 31W has a property of penetrating lightin the entire visible light range, it is possible to improve thesensitivity of the phase difference detection pixels 32.

When some of the W pixels 31W are substituted with the phase differencedetection pixels 32, the light intensity received by the phasedifference detection pixels 32 may be excessively increased due to theproperty of the color filter included in the W pixel 31W, and light maybe leaked to the imaging pixels 31 which are adjacent to the phasedifference detection pixels 32.

When such a leakage of light is not allowed, some of the R pixels 31R,the G pixels 31G, or the B pixels 31B are substituted with the phasedifference detection pixels 32, and thus, it is possible to decrease theleakage of light to the imaging pixel 31 which is adjacent to the phasedifference detection pixels 32, by the property of only penetratinglight with a specific color of the color filter included in the phasedifference detection pixels 32.

The color of the color filter included in the phase difference detectionpixels 32 is not limited to the same color of the R pixel, the G pixel,the B pixel, and the W pixel, and may be a color which is the same asany one color of the color filter included in the imaging pixel 31.

Configuration Example of Electronic Apparatus

Next, a configuration example of an electronic apparatus to which thepresent technology is applied will be described with reference to FIG.36.

An electronic apparatus 500 shown in FIG. 36 includes an optical lens501, a shutter device 502, a solid-state imaging device 503, a drivingcircuit 504, and a signal processing circuit 505. FIG. 36 shows aconfiguration in a case of providing the CMOS image sensor 10 includingthe pixels of the embodiments in the electronic apparatus (for example,a digital still camera), as the solid-state imaging device 503.

The optical lens 501 images image light (incident light) from a subjecton an imaging surface of the solid-state imaging device 503.Accordingly, signal charges are accumulated in the solid-state imagingdevice 503 for a given time period. The shutter device 502 controls alight emission period and a light shielding period with respect to thesolid-state imaging device 503.

The driving circuit 504 supplies a driving signal for controlling asignal transmission operation of the solid-state imaging device 503 anda shutter operation of the shutter device 502. The solid-state imagingdevice 503 performs signal transmission by the driving signal (timingsignal) supplied from the driving circuit 504. The signal processingcircuit 505 performs various signal processes with respect to the signaloutput from the solid-state imaging device 503. A moving image signalsubjected to the signal process is stored in a storage medium such as amemory and is output to a monitor.

The electronic apparatus 500 includes a lens driving unit (not shown)which drives the optical lens 501 in an optical axis direction thereof.The lens driving unit configures a focus mechanism for performing focusadjustment, with the optical lens 501. In the electronic apparatus 500,various control operations such as a control operation of the focusmechanism or a control operation of the constituent elements describedabove are performed by a system controller (not shown).

Regarding the control operation of the focus mechanism, an arithmeticprocess of calculating a deviation direction and a deviated amount ofthe focus is, for example, performed in the signal processing circuit505, based on a focus detection signal output from the phase differencedetection pixel of the solid-state imaging device of the presenttechnology. By receiving this arithmetic result, the system controllerperforms the focus control operation of moving the optical lens 501 inthe optical axis direction thereof through the lens driving unit to setthe focused state.

According to the electronic apparatus 500 of the embodiment of thepresent technology, it is possible to optimize the sensitivity of theimaging pixel and the AF performance of the phase difference detectionpixel in the solid-state imaging device 503, and as a result, imagequality is improved.

The embodiments of the present technology are not limited to theembodiments described above, and various modifications can be performedwithin a range not departing from a scope of the present technology.

The present technology can be configured as follows.

(1) A solid-state imaging device including:

an imaging pixel including a photoelectric conversion unit whichreceives incident light; and

a phase difference detection pixel including the photoelectricconversion unit and a light shielding unit which shields some of thelight incident to the photoelectric conversion unit,

in which the imaging pixel further includes a high refractive index filmwhich is formed on the upper side of the photoelectric conversion unit,and

the phase difference detection pixel further includes a low refractiveindex film which is formed on the upper side of the photoelectricconversion unit.

(2) The solid-state imaging device according to (1),

in which the imaging pixel and the phase difference detection pixelinclude color filter layers which are respectively formed on upperlayers of the high refractive index film and the low refractive indexfilm, and

the high refractive index film and the low refractive index filmfunction as a flattening film.

(3) The solid-state imaging device according to (2),

in which the low refractive index film is formed to cover the highrefractive index film and functions as the flattening film.

(4) The solid-state imaging device according to (2),

in which the high refractive index film is formed to cover the lowrefractive index film and functions as the flattening film.

(5) The solid-state imaging device according to any one of (1) to (4),

in which a refractive index of the high refractive index film is higherthan a refractive index of the low refractive index film, by a valueequal to or greater than 0.1.

(6) The solid-state imaging device according to (5),

in which the refractive index of the high refractive index film is setas a value from 1.5 to 2.0.

(7) The solid-state imaging device according to (5),

in which the refractive index of the low refractive index film is set asa value from 1.1 to 1.5.

(8) The solid-state imaging device according to any one of (1) to (7),

in which any one or both of the high refractive index film and the lowrefractive index film are formed of a material having a photosensitiveproperty.

(9) The solid-state imaging device according to any one of (1) to (8),

in which the high refractive index film or the low refractive index filmis formed to have a cross-sectional shape as a shape of a convex lens.

(10) The solid-state imaging device according to any one of (1) to (9),

in which the imaging pixel and the phase difference detection pixelinclude microlenses on the upper side of the color filter layers, and

the microlenses are formed in the same manner, in the imaging pixel andthe phase difference detection pixel.

(11) A manufacturing method of a solid-state imaging device whichincludes an imaging pixel including a photoelectric conversion unitwhich receives incident light, and a phase difference detection pixelincluding the photoelectric conversion unit and a light shielding unitwhich shields some of the light incident to the photoelectric conversionunit, the method including:

forming a high refractive index film on the upper side of thephotoelectric conversion unit in the imaging pixel; and

forming a low refractive index film on the upper side of thephotoelectric conversion unit in the phase difference detection pixel.

(12) An electronic apparatus including:

a solid-state imaging device including

-   -   an imaging pixel including a photoelectric conversion unit which        receives incident light, and    -   a phase difference detection pixel including the photoelectric        conversion unit and a light shielding unit which shields some of        the light incident to the photoelectric conversion unit,    -   in which the imaging pixel further includes a high refractive        index film which is formed on the upper side of the        photoelectric conversion unit, and    -   the phase difference detection pixel further includes a low        refractive index film which is formed on the upper side of the        photoelectric conversion unit.

In addition to the configuration described above, the present technologycan be configured as follows.

(1) A solid-state imaging device including:

an imaging pixel including a photoelectric conversion unit whichreceives incident light and a color filter which is formed on the upperside of the photoelectric conversion unit; and

a phase difference detection pixel including the photoelectricconversion unit, the color filter, and a light shielding unit whichshields some of the light incident to the photoelectric conversion unit,

in which the color filter included in the phase difference detectionpixel is formed so as to have a film thickness to be smaller than a filmthickness of the color filter included in the imaging pixel.

(2) The solid-state imaging device according to (1),

in which the color filter included in the phase difference detectionpixel is formed as a color filter with the same color as one of colorsof the color filter included in the imaging pixel.

(3) The solid-state imaging device according to (2),

in which the color filter included in the phase difference detectionpixel is formed as any one of a red color filter, a green color filter,and a blue color filter.

(4) The solid-state imaging device according to (2),

in which the color filter included in the phase difference detectionpixel is formed as a white color filter.

(5) A manufacturing method of a solid-state imaging device whichincludes an imaging pixel including a photoelectric conversion unitwhich receives incident light and a color filter which is formed on theupper side of the photoelectric conversion unit, and a phase differencedetection pixel including the photoelectric conversion unit, the colorfilter, and a light shielding unit which shields some of the lightincident to the photoelectric conversion unit, the method including:

forming the color filter included in the phase difference detectionpixel so as to have a film thickness to be smaller than a film thicknessof the color filter included in the imaging pixel.

(6) The manufacturing method of a solid-state imaging device accordingto (5) further including:

exposing a color filter material by using a first reticle having a firstexposure pattern of exposing an area in which the imaging pixel isformed; and exposing the color filter material with the light exposureconditions different from the case of using the first reticle, by usinga second reticle having a second exposure pattern of exposing an area inwhich the phase difference detection pixel is formed.

(7) The manufacturing method of a solid-state imaging device accordingto (5) further including:

exposing the color filter material by using a gray scale mask having afirst exposure pattern of exposing an area in which the imaging pixel isformed, and a second exposure pattern of exposing an area in which thephase difference detection pixel is formed and having lighttransmittance different from that of the first exposure pattern.

(8) An electronic apparatus including:

a solid-state imaging device including

-   -   an imaging pixel including a photoelectric conversion unit which        receives incident light and a color filter which is formed on        the upper side of the photoelectric conversion unit; and    -   a phase difference detection pixel including the photoelectric        conversion unit, the color filter, and a light shielding unit        which shields some of the light incident to the photoelectric        conversion unit,    -   in which the color filter included in the phase difference        detection pixel is formed so as to have a film thickness to be        smaller than a film thickness of the color filter included in        the imaging pixel.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An imaging device comprising: an imaging pixelincluding a first photoelectric conversion unit that receives incidentlight; a phase difference detection pixel including a secondphotoelectric conversion unit that receives incident light; a lightshielding member that shields the photoelectric conversion unit of thephase difference detection pixel from some light incident on the phasedifference detection pixel; a flattening film formed on an upper side ofthe imaging pixel, the phase difference detection pixel, and lightshielding member; and a color filter layer formed on an upper side ofthe flattening film, wherein the color filter layer includes a firstcolor filter located on the first photoelectric conversion unit and asecond color filter located on the second photoelectric conversion unit,and wherein the second color filter is thinner than the first colorfilter based on a sensitivity of the phase difference detection pixel.2. The imaging device according to claim 1, wherein the imaging pixelfurther includes a refractive index film that is formed on an upper sideof the first photoelectric conversion unit.
 3. The imaging deviceaccording to claim 2, wherein the phase difference detection pixelfurther includes a low refractive index film that is formed on an upperside of the second photoelectric conversion unit, wherein the lowrefractive index film has a lower refractive index than the refractiveindex film.
 4. The imaging device according to claim 3, wherein arefractive index of the refractive index film is higher than arefractive index of the low refractive index film, by a value equal toor greater than 0.1.
 5. The imaging device according to claim 3, whereinthe refractive index of the refractive index film is set as a value from1.5 to 2.0.
 6. The imaging device according to claim 3, wherein therefractive index of the low refractive index film is set as a value from1.1 to 1.5.
 7. The imaging device according to claim 3, wherein any oneor both of the refractive index film and the low refractive index filmare formed of a material having a photosensitive property.
 8. Theimaging device according to claim 3, wherein the refractive index filmor the low refractive index film is formed to have a cross-sectionalshape as a shape of a convex lens.
 9. The solid-state imaging deviceaccording to claim 3, wherein the imaging pixel and the phase differencedetection pixel include microlenses on an upper side of the color filterlayer, and the microlenses are formed in the same manner, in the imagingpixel and the phase difference detection pixel.
 10. The imaging deviceaccording to claim 2, wherein the flattening film is formed to cover therefractive index film.
 11. The imaging device according to claim 1,wherein the sensitivity of the phase difference detection pixel is lowerthan a sensitivity of the imaging pixel.
 12. The imaging deviceaccording to claim 11, wherein the flattening film is a low refractiveindex film having a refractive index of 1.1 to 1.5.
 13. The imagingdevice according to claim 1, wherein a pixel of a first color is thephase difference detection pixel, and wherein the imaging pixel is ofthe first color.